Traveling nut limit stop



Jan. 25, 1949.

w. s. HALL, JR TRAVELING NUT LIMIT STOP 2 Sheets-Sheet l Filed Feb. 20, 1946 SYWMVWD WALTER S. HALL, JR.

Patented Jan. 25, 1949 Walter and 1105 to the flnit'ed s esm by the-seeretasyer the Navy" Application Eehruat-y zfl, 1946,. Serial No; sat-ass My invention relates to mechanical'stops and].

rotten. (Cl. IL-424.3

more particularly to travelling nut "stops.

such'as are used'i'n traihi'iig'fgear for nydriopnones, In the application of' hydrobhoiies to dete mine the presence and direction of. an under Watfl' noise r e, the hyd'rbnhonemu'stfb "rotated about a vertical genera y accomplished by means of 'acrank-rotated worm driving a worm gear'on the'aydropnonesham- The required traverse of the. hYdrophone -in' operation is greater than Hi0 'cl'egrees. Howeven;

rotation in any one direction must be limited in order toavoid tangli'nghf control cable's pass.- ing down the hydro'phone shaft) Otherwi'sa'icon tinned rotation in a single direction would so entangle these cables that they would be dam:

aged or destroyed in a short time." It 'has'benf proposed to use a fiexiblepinl'imitstop con'i prising a radially projecting pin mounted by" a lost motion connection on the hydrophone shaft and adapted to engage a'fixecrstop. Thism'echanism has been found unsatisfactory;for -it prO f vides a maximimi of 400=-degreestraverse and i"- objectionably noisy in operation. I'ri -particu the metal pin striking the -eta stop-Hike distinct clank thatcan be'heoty'on hydrophones, but by listening devices on e vessels, thereby not onl yi-mpairing the-opera of the hydrophorie; but also revali" fthe pres-'-' ence of the ship uponwhi'oh'it is menses;

It has been further proposed t u'se aerate-rise nut limit stop to avoidthe above mentioned 1m"- itations of a flexible pinl-imit -stop A ortion of the Worm shaft is provided with threads having a pitch of about eight'to the inch. A nut engag over, lubricated-so that the travelling-nut'freeaesthe. engagement of the metallic outwith the metallic stop'produees; objectionable clan-kv similar to that with the flexible 19in:v W

Inen etiort to avoid the disadvantages of the travelling nut tyne stop, it has been proposed to iorm a deep circumferential groove of rectanau lar cross section in I Y provided to limit motionof the travelling nut,

and-each end of the nut provided With'anannnlargprojection of rectangular cross section adapted to fitsnugly into this groove; The traveling nut mechanism is enclosed in a casing adaptedto be iii-lied with. lubricant so; that the annular. projections on the-travelling nut and the oorrespond inn-grooves in the baseoi the collars oi the shaft. will act as hydraulicpistons and cylinders, re-

spectively, the; lubricant being trap-pcd in the,

g-roo e and servingto-cushion the impact of the travelling nut with; the coliars. This proposal-v been ioundun-sattsfac-tory, iorthe elosewtoi erances requiredbetweenthe annular projections otthenut: and the-grooves on the-collar could not be snain-tainedas a-practioal matter. Morethe gear frequently becomes improperly spite thesupposed hydraulic cushion i have: found that the above mentioned-disad-- vanta'aes ottravelling nut. stops for hydrophones may be avoided by the use oi'ia resilient irig these threads is held against rotation and adapted to traverse the shaft as the latter is rotated, stops being provided to limlt the extent of traverse. Upon engagement.rofthe travelling nut with the stop provided at either end of its travel, the Worm shaft'is heldegain'st further rotation in that direction, thereby limiting rotary movement of the hydrophones; The traveling nut. limit has been found to be an imnrovement' over the flexible pin limit stop' in that it provides greater traverse, for examplaabout 630 degrees. However, it has been found infoperatibnf that when the travelling nut engages the stop'it may freeze on the worm shaft, making it impossible to turn the shaft in either direction. This freezing has been found so severe that the crank handle on the shaft has been broken ofiin an efiort to free the shaft and rotate it in the. oppositedi'rec'tion. Moreover, the travelling nut lirriit, like the flexible pin, has proven to be noisy as member-"on each of the limit stopsadaptedto coact'with annular projections on each side of the travelling nut. Whenthe resflient surface: is first 'struck 'bythe-projecting not; the turning eifort. required increases, thereby the operator in advance that he is apprgaaching the limit of travel. However; ibis-necessary to continuetnrning the shaft to the absolute limit, the travelling nut will not freeze and the shaft will remain-free to turrr when retltaoted from the position with the nut against the'ston Furthe-rmore,-'-the objectionable no-ise' ii-rherent i n pr'evious limit devices is eliminated and the-reduced efiiciency'of the hydrophone associated with-' this noise," together with the possibility J of pick-up by enemy craft, is eliminated."

It istherefore the objector this invention to; provide a travelling .nutlimit stop suitable for the faceof eachof the. eollars which will not freeze or bind when forced against the limit.

Furthermore, it is an object of this invention to provide a travelling nut limit stop which forewarns the operator when the limit is approached.

Other objects and aspects of this invention will be apparent from the following description and claim:

In the figures:

Figure 1 shows an exploded view of the complete gear box and rotating unit for a hydrophone.

Figure 2 shows a detailed cross-sectional view of my travelling nut limit stop.

Referring now to Figure l, the hydrophone is mounted on vertical shift I which extends through the hull of the vessel to the operating shaft l0. Operating shaft I is connected to hydrophone shaft l by means of worm shaft 5 and worm wheel 4. Shaft I is mounted on ball bearings 3 and shaft I G is mounted on ball bearings 9. Shaft l0 isprovided with stop nut 6 which is in threaded engagement with threads l3 on shaft 10. Stop nut 6 is provided with lug II adapted to slide in a suitable slot or groove provided in a fixed portion of the apparatus to hold the nut against rotation, but which will permit movement of the nut axially of the shaft due to its engagement with the threads l3, until it meets either one of the stops 7 or 8. The entire assembly is enclosed in gear case 2 which acts as a receptacle for grease and protects the mechanism from external damage.

Figure 2 shows in further detail the method whereby my invention limits rotation. In the figure, threaded portion I3 of shaft [0 is provided with an annular shoulder or collar 1 while at. the

other end of the threaded portion there is provided a similar though removable shoulder 'or collar 8. An annular grove l5 of rectangular cross section is provided in the surface of each of the collars l and 8 which faces threaded por-' tion 13 of shaft l0. At each end of the travelling nut 6 there is provided an annular projection I 4 of rectangular cross section adapted to fit relatively snugly into the groove l5 of the collars l and 8. An annular cushion l2 formed of soft' resilient material, such as neoprene, is positioned in each of the annular grooves l5 of collars l and 8 as shown. v

Upon reaching the end of its traverse in either direction, one projection M of travelling nut 6' engages a neoprene ring l2 so that the impact 1 of the nut with the stop is cushioned and no freezing occurs. The stopping of the travelling nut is thus gradual and the increased resistance associated'with turning of the operating shaft l0 can be felt by the operator one-quarter to onehalf a turn before the final stop is reached. The operator is thus forewarned in time to stop turning the handle before the travelling nut comes up firmly against the stop. During this period,

the round neoprene ring l2 becomes distorted and is pressed into the rectangular groove 15.

If the exigencies of the situation demand that the hydrophone be turned further against the stop, the operator may intentionally do so, thereby obtaining one-quarter to one-half a turn of additional rotation. This rotation, beinginfre quent, has little effect on cables and other ,apparatus in the hydrophone shaft. No freezing will occur in this case'as the neoprene ring acts to distribute the pressure exerted by-the limit collar, thereby providing a substantial resistance to motion without the concentrated and unbalanced forces which lead to freezing.

The neoprene ring, interposed between the travelling nut 6 and the limit collars 7 and 8, not only prevents freezing but also eliminates the objectionable noise that heretofore has resulted from impact of the metal nut with the metal collars. This avoids the noise in the hydrophone which previously resulted from such impact and prevents the generation of noise which might be picked up by enemy vessels. Furthermore, the shock incident to metal-to-metal impact is avoided and jarring of the equipment prevented. In general, it is considered preferable to use a circular section in the neoprene ring and a rectangular section in the annular collar grooves. However, this invention is not limited to the particular shape of the ring, or to confining the ring in a groove. It will likewise be understood that while neoprene is desirable because of its oil resistant properties, other rubber-like or rubber compositions may be used, the principal requirements being that it yield without permanent deformation and produce minimum noise when struck.

It has been found that the neoprene rings are not damaged in any way by repeated impact of the travelling nut. Extensive tests over a period of several weeks of normal operation failed to produce any visible effect on the rings.

It will be evident to those skilled in the art that the traverse of the travelling nut may be limited by collars provided on the Casing or other member adjacent to the collars. Furthermore, the stops may be made adjustable by screws or other devices provided for the purpose.

This invention is capable of Wide variation from the particular form described herein, its scope being defined in the appended claim.

I claim:

A travelling nut limit stop comprising a shaft, a casing rotably supporting the same, said shaft having-a threaded portion, a nut threaded on said threaded portion, an annular projection on each end of" said nut, means on said nut and casing preventing rotation of said nut, stops mounted on said shaft at the opposite ends of saidthreaded portion, said stops having annular grooves facing said annular projections, respectively, and in alignment therewith and resilient annular members in said grooves adapted to engage said annular projections, respectively, to cushion the engagement of said nut against either of said stops.

WALTER S. HALL, JR.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 1,301,137 La Barre Apr. 22, 1919 1,632,927 Shackelford June 21, 1927 1,634,677 Miller July 5, 1927 1,939,933 Wacker 1 Dec. 19, 1933 2,057,187 1 Gallasch Oct. 13, 1936 2,084,845 Holmes June 22, 1937 2,245,457 Brassell June 10, 1941 2,297,137 Fennema Sept. 29, 1942 2,336,133 Thornhill Dec. 7, 1943 2,349,370 Orner May 23, 1944 2,356,861 Link Aug. 29, 1944 2,398,841 Morris Apr. 23, 1946 

